Personally, I would send her the box and believe that she did send the money. I would have a clear conscience knowing that I had trusted an old friend and made good on my side of the deal.
A box is a box. A friendship is something else.
If in fact she did pull a fast one on me, she is the one losing sleep from a guilty conscience…… not me.

The early bird gets the worm but its the second mouse that gets the cheese.